Question concerning one sibling having power of attorney for an aging parent.?

My sister is an attorney lives in Washington state. My mother and I live in Oregon. Mom was diagnosed with Alzheimer's about 3 years ago, my sister got a complete power of attorney over her which covers everything. I went along with it because I figured my sister is a lawyer so she knows about these situations. I live with my mom and have been her caretaker pretty much every way. On Labor Day mom fell and had to be hospitalized but she didn't suffer any severe injuries and will soon be released from the hospital, they are keeping her a few extra days for observation due to her age. The social worker has advised my sister and I to put her into a secure nursing facility until there is a space available at a memory care home. My sister wants to move her to Washington state because she feels they have better facilities than Oregon. I am not in agreement with this and feel that my mother should remain in Oregon because she has friends here as well as it making it more efficient for me to visit and be with her. When the power of attorney was drawn up, my sister WAS an Oregon resident but has lived in Washington state for over a year now. She occasionally takes my mother to medical appointments and every once in a while will stop by to visit and clean house a little. Other than that and phone calls now and again she has little contact with her. Is there ANY legal procedures I can go forward with to prevent this move from happening? Any advice would be well appreciated. Thank you!